Question about O_APPEND | O_DIRECT

[Tao Lyu <tao.lyu@xxxxxxx>]

Hi,

Sorry to bother you here.

I'm using NFS and realize it doesn't support opening a file with "O_DIRECT | O_APPEND".

After checking the source code, 
I found it has one function that checks explicitly whether there is a combination flag of "O_APPEND | O_DIRECT".
If so, it will return invalid arguments.

int nfs_check_flags(int flags)
{
    if ((flags & (O_APPEND | O_DIRECT)) == (O_APPEND | O_DIRECT))
        return -EINVAL;

    return 0;
}

But I don't understand why NFS doesn't support this flag combination.
I'd appreciate it if someone could explain this to me.

Thanks in advance.

Best,
Tao